Photolithography has long been employed in the semiconductor industry to delineate circuit patterns. A layer of a photoresist is applied to the substrate to be patterned and the layer exposed to light of a suitable wavelength through a mask defining the pattern. The photoresist changes its solubility when exposed to the light; positive resists become more soluble by the action of the light, usually by a degradation reaction, and negative resists become more insoluble, usually as a result of crosslinking reactions. The substrate is then contacted with a developer solvent which removes the more soluble portions of the resist. The substrate can then be etched so as to remove portions of the substrate not covered by the photoresist. After etching, the remaining resist is stripped with a solvent.
With the ever increasing miniaturization of circuit patterns, electron beam exposure has begun to be employed instead of light exposure. Electron beams, by virtue of their shorter effective wavelengths and greater depth of focus, can record information at higher densities and resolution than can light beams. However, while some photoresists are also useful as electron beam resists, most are not and a search has been continued to find materials suitable as electron beam resists. Most known electron beam resists are positive acting resists. However, since the electronics industry is more familiar with the use of negative resists, and since negative resists generally are more sensitive, more etch resistant and require less control during processing, negative electron beam resists that have good sensitivity to electron beam radiation and that show good contrast between soluble and insoluble portions after exposure and development, would be preferred.